Power Supply issues

hey i have this computer and the power supply keeps going bad. The first time i replaced it with the same voltage and it worked for a few monthes and went bad again. This time i got a bigger power supply and now the computer boots up to the "windows didnt shut down completely do you want to start in safe mode" screen (i run xp) and then the keyboard stops responding and i cant get past that screen.

The keyboard works on boot up b/c i can get into the setup menu with F2 but once it gets to that screen...........nothing

anyone have a similar problem????